Chapter 1
gaze=
You can see the full moon only once in about a month’s time. It is Full moon night or Poornima. A fortnight later, you cannot see it at all. It is a New moon night or Amavasya. On this day, you can watch the night sky best, provided it is a clear night.
The sun, the moon and all those objects shining in the night sky are called celestial bodies.
They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars. The sun is a star.
While watching the night sky, you may notice various patterns formed by different groups of stars. These are called constellations. Ursa Major or Big Bear is one such constellation. One of the most easily recognisable constellation is the small bear or Saptarishi (Sapta-seven, rishi-sages). It is a group of seven stars (Figure 1.1) that forms a part of the large Ursa Major Constellation.
The North star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky. We can locate the position of the Pole Star with
the help of the Saptarishi. Look at Figure 1.1. You will notice that, if an imaginary line is drawn joining the pointer stars and extended further, it will point to the Pole Star.
Inner planets - very close to the sun. They are made up of rocks
Outer Planets - Very-very far from the sun and are huge planets made up of gases and liquids.
Sun provides the pulling force that binds the solar system.
Till recently (August 2006), Pluto was also considered a planet. However, in a meeting of the International Astronomical Union, a decision was taken that Pluto like other celestial objects (Ceres, 2003 UB313) discovered in recent past may be called ‘dwarf planets.”
Some of the Indian satellites in space are INSAT, IRS, EDUSAT, etc.
Chapter 2
reckoned=calculated
All parallel circles from the equator up to the poles are called parallels of latitudes. Latitudes are measured in degrees.
The equator represents the zero degree latitude. Since the distance from the equator to either of the poles is one-fourth of a circle round the earth, it will measure 1/4th of 360 degrees, i.e. 90°. Thus, 90 degrees north latitude marks the North Pole and 90 degrees south latitude marks the South Pole.
(i) Tropic of Cancer (23 ° N) in the Northern Hemisphere. (ii) Tropic of Capricorn (23 ° S) in the Southern Hemisphere. (iii) Arctic Circle at 66 ° north of the equator. (iv) Antarctic Circle at 66 ° south of the equator.
HEAT ZONES OF THE EARTH
The mid-day sun is exactly overhead at least once a year on all latitudes in between the Tropic of Cancer and the Tropic of Capricorn. This area, therefore, receives the maximum heat and is called the Torrid Zone.
The angle of the sun’s rays goes on decreasing towards the poles. As such, the areas bounded by the Tropic of Cancer and the Arctic Circle in the Northern Hemisphere, and the Tropic of Capricorn and the Antarctic Circle in the Southern Hemisphere, have moderate temperatures. These are, therefore, called Temperate Zones.
all countries decided that the count should begin from the meridian which passed through Greenwich, where the British Royal Observatory is located. This meridian is called the Prime Meridian. Its value is 0° longitude and from it we count 180° eastward as well as 180° westward. The Prime Meridian and 180° meridian divide the earth into
two equal halves, the Eastern Hemisphere and the Western Hemisphere. Therefore, the longitude of a place is followed by the letter E for the east and W for the west. It is, however, interesting to note that 180° East and 180° West meridians are on the same line.
Local time can be reckoned by the shadow cast by the sun, which is the shortest at noon and longest at sunrise and sunset.
When the Prime Meridian of Greenwich has the sun at the highest point in the sky, all the places along this meridian will have mid-day or noon.
As the earth rotates from west to east, those places east of Greenwich will be ahead of Greenwich time and those to the west will be behind it (Figure 2.8). The rate of difference can be calculated as follows. The earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes. Thus, when it is 12 noon at Greenwich, the time at 15° east of Greenwich will be 15 *4 = 60 minutes, i.e., 1 hour ahead of Greenwich time, which means 1 p.m. But at 15° west of Greenwich, the time will be behind Greenwich time by one hour, i.e., it will be 11.00 a.m. Similarly, at 180°, it will be midnight when it is 12 noon at Greenwich.
there will be a difference of about 1 hour and 45 minutes in the local times of Dwarka in Gujarat and Dibrugarh in Assam. It is, therefore, necessary to adopt the local time of some central meridian of a country as the standard time for the country. In India, the longitude of 82 ° E (82° 30'E) is treated as the standard meridian. The local time at this meridian is taken as the standard time for the whole country. It is known as the Indian Standard Time (IST).
The earth has been divided into twenty-four time zones of one hour each. Each zone thus covers 15° of longitude.
Chapter 3
The axis of the earth which is an imaginary line, makes an angle of 66 ° with its orbital plane. The plane formed by the orbit is known as the orbital plane. The earth receives light from the sun. Due to the spherical shape of the earth, only half of it gets light from the sun at a time (Figure 3.2). The portion facing the sun experiences day while the other half away from the sun experiences night. The circle that divides the day from night on the globe is called the circle of illumination. This circle does not coincide with the axis as you see in the Figure 3.2. The earth takes about 24 hours to complete one rotation around its axis. The period of rotation is known as the earthday. This is the daily motion of the earth.
What would happen if the earth did not rotate? The portion of the earth facing the sun would always experience day, thus bringing continuous warmth to the region. The other half would remain in darkness and be freezing cold all the time. Life would not have been possible in such extreme conditions.
The second motion of the earth around the sun in its orbit is called revolution. It takes 365 days (one year) to revolve around the sun. We consider a year as consisting of 365 days only and ignore six hours for the sake of convenience.
A year is usually divided into summer, winter, spring and autumn seasons. Seasons change due to the change in the position of the earth around the sun.
On 21st March and September 23rd, direct rays of the sun fall on the equator. At this position, neither of the poles is tilted towards the sun; so, the whole earth experiences equal days and equal nights. This is called an equinox.
Thus, you find that there are days and nights and changes in the seasons because of the rotation and revolution of the earth respectively.
chapter 5
The surface of the earth is a complex zone in which three main components of the environment meet, overlap and interact. The solid portion of the earth on which we live is called the Lithosphere. The gaseous layers that surround the earth, is the Atmosphere, where oxygen, nitrogen, carbondioxide and other gases are found. Water covers a very big area of the earth’s surface and this area is called the Hydrosphere. The Hydrosphere comprises water in all its forms, that is, ice, water and water vapour.
The Biosphere is the narrow zone where we find land, water and air together, which contains all forms of life.
SA lies mostly in the Southern Hemisphere. Which two oceans surround it on the east and the west? The Andes, world’s longest mountain range, runs through its length from north to south (Figure 5.1). South America has the world’s largest river, the Amazon.
Antarctica, completely in the Southern Hemisphere, is a huge continent. The South Pole lies almost at the centre of this continent. As it is located in the South Polar Region, it is permanently covered with thick ice sheets. There are no permanent human settlements. Many countries have research stations in Antarctica. India also has research stations there. These are named as Maitri and Dakshin Gangotri.
More than 97% of the Earth’s water is found in the oceans and is too salty for human use. A large proportion of the rest of the water is in the form of icesheets and glaciers or under the ground and a very small percentage is available as fresh water for human
The ocean waters are always moving. The three chief movements of ocean waters are the waves, the tides and the ocean currents. The five major oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean, in order of their size
The coastline of Atlantic Ocean is highly indented. This irregular and indented coastline provides ideal location for natural harbours and ports. From the point of view of commerce, it is the busiest Ocean.
The Indian Ocean is the only ocean named after a country, that is, India. The shape of ocean is almost triangular.
The Arctic Ocean is located within the Arctic Circle and surrounds the North Pole. It is connected with the Pacific Ocean by a narrow stretch of shallow water known as Berring strait. It is bound by northern coasts of North America and Eurasia.
The atmosphere extends up to a height of about 1,600 kilometres. The atmosphere is divided into five layers based on composition, temperature and other properties. These layers starting from earth’s surface are called the troposphere, the stratosphere, the mesosphere, the thermosphere and the exosphere.
Carbon dioxide, though present in minute amount, is important as it absorbs heat radiated by the earth, thereby keeping the planet warm. It is also essential for the growth of plants.
You know, the climbers experience problems in breathing due to this decrease in the density of air. They have to carry with them oxygen cylinders to be able to breathe at high altitudes. The temperature also decreases as we go upwards. The atmosphere exerts pressure on the earth. This varies from place to place. Some areas experience high pressure and some areas low pressure. Air
moves from high pressure to low pressure. Moving air is known as wind.
Similarly earth’s surface may be changed due to natural calamities like earthquakes. For example, there could be submergence of land, as happened in the case of Tsunami recently. Parts of Andaman & Nicobar islands were submerged under water.
Chapter 6
Generally a steep hill with an elevation of more than 600 metres is termed as a mountain .
The second,or the externalprocess is the continuous wearing down and rebuilding of the land surface. The wearing away of the earth’s surface is called erosion. The surface is being lowered by the process of erosion and rebuilt by the process of deposition. These two processes are carried out by running water, ice and wind. Broadly, we can group different landforms depending on elevation and slope as mountains, plateaus and plains.
The Himalayas, the Alps and the Andes are mountain ranges of Asia, Europe and South America, respectively
There are three types of mountains- Fold Mountains, Block Mountains and the Volcanic Mountains. The Himalayan Mountains and the Alps are young fold mountains with rugged relief and high conical peaks. The Aravali range in India is one of the oldest fold mountain systems in the world. The range has considerably worn down due to the processes of erosion. The Appalachians in North America and the Ural mountains in Russia (Figure 5.1) have rounded features and low elevation. They are very old fold mountains.
Block Mountains are created when large areas are broken and displaced vertically. The uplifted blocks are termed as horsts and the lowered blocks are called graben. The Rhine valley and the Vosges mountain in Europe are examples of such mountain systems. Locate them on the world map in the atlas and find out some more examples of this type of landforms.
Volcanic mountains are formed due to volcanic activity. Mt.Kilimanjaro in Africa and Mt.Fujiyama in Japan are examples of such mountains.
Mountains are very useful. The mountains are a storehouse of water. Many rivers have their source in the glaciers in the mountains. Reservoirs are made and the water is harnessed for the use of people. Water from the mountains is also used for irrigation and generation of hydro-electricity. The river valleys and terraces are ideal for cultivation of crops. Mountains have a rich variety of flora and fauna. The forests provide fuel, fodder, shelter and other products like gum, raisins, etc. Mountains provide an idyllic site for tourists. They visit the mountains for their scenic beauty. Several sports like paragliding, hang gliding, river rafting and skiing are popular in the mountains.
PLATEAUS
A plateau is an elevated flat land. It is a flat-topped table land standing above the surrounding area. A plateau may have one or more sides with steep slopes. The height of plateaus often varies from few hundred metres to several thousand metres. Plateaus, like mountains may be young or old. The Deccan plateau in India is one of the oldest plateaus. The East African Plateau in Kenya, Tanzania and Uganda and the Western plateau of Australia are other
examples. The Tibet plateau (Figure 5.1, p.31) is the highest plateau in the world with a height of 4,000 to 6,000 metres above the mean sea level.
Plateaus are very useful because they are rich in mineral deposits. As a result, many of the mining areas in the world are located in the plateau areas.
In India huge reserves of iron, coal and manganese are found in the Chhotanagpur plateau.
In the plateau areas, there may be several waterfalls as the river falls from a great height. In India, the Hundru falls in the Chhotanagpur plateau on the river Subarnarekha and the Jog falls in Karnataka are examples of such waterfalls. The lava plateaus are rich in black soil that are fertile and good for cultivation. Many plateaus have scenic spots and are of great attraction to tourists.
PLAINS
Plains are large stretches of flat land. They are, generally, not more than 200 metres above mean sea level.
Most of the plains are formed by rivers and their tributaries. The rivers flow down the slopes of mountains and erode them. They carry forward the eroded material. Then they deposit their load consisting of stones, sand and silt along their courses and in their valleys. It is from these deposits that plains are formed.
Chapter 7
India has an area of about 3.28 million sq. km.
The north-south extent from Kashmir to Kanyakumari is about 3,200 km. And the east-west extent from Arunachal Pradesh to Kuchchh is about 2,900 km.
Large countries which stretch extensively from
east to west do not have a single Standard Time for the whole country. The USA and Canada have seven and six time zones respectively
The Tropic of Cancer (23°30'N) passes almost halfway through the country (Figure 7.2). From south to north, main land of India extends between 8°4'N and 37°6'N latitudes. From west to east, India extends between 68°7'E and 97°25'E longitudes. If we divide the world into eastern and western hemispheres, which hemisphere would India belong to? Due to great longitudinal extent of about 29°, there could be a wide differences in local time of places located at two extreme points of India.
local time changes by four minutes for every one degree of longitude.
Sri Lanka is separated from India by the Palk Strait.
Alluvial deposits : These are very fine soils, brought by rivers and deposited in the river basins.
Tributary : A river or stream which contributes its water to a main river by discharging it into main river from either side
The northernmost is the Great Himalaya or Himadri. The world’s highest peaks are located in this range. Middle Himalaya or Himachal lies to the south of Himadri. Many popular hill stations are situated here. Find out the names of five hill stations. The Shiwalik is the southernmost range.
The Western Ghats or Sahyadris border the plateau in the west and the Eastern Ghats provide the eastern boundary. While the Western Ghats are almost continuous, the Eastern Ghats are broken and uneven (Figure 7.3). The plateau is rich in minerals like coal and iron-ore.
To the West of the Western Ghats and the East of Eastern Ghats lie the Coastal plains.
Corals are skeletons of tiny marine
animals called Polyps. When the living polyps die, their skeletons are left. Other poplyps grow on top of the hard skeleton which grows higher and higher, thus forming the coral islands.
The eastern Coastal plains are much broader. There are a number of east flowing rivers. The rivers Mahanadi, Godavari, Krishna and Kaveri drain into the Bay of Bengal. These rivers have formed fertile deltas at their mouth. The Sunderban delta is formed where the Ganga and Brahmaputra flow into the Bay of Bengal.
Two groups of islands also form part of India. Lakshadweep Islands are located in the Arabian Sea . These are coral islands located off the coast of Kerala. The Andaman and the Nicobar Islands lie to the southeast of the Indian mainland in the Bay of Bengal. Do you know which group of islands were affected by the Tsunami in 2004?
Chapter 8
weather is about day to day changes in the atmosphere. It includes changes in temperature, rainfall and sunshine etc.
HOT WEATHER SEASON OR SUMMER
Temperature becomes very high. Hot and dry winds called loo, blow during the day.
Temperature becomes very high. Hot and dry winds called loo, blow during the day.
SOUTH WEST MONSOON SEASON OR RAINY SEASON
This season is marked by the onset and advance of monsoon. The winds blow from Arabian Sea and Bay of Bengal towards the land. They carry moisture with them. When these winds strike the mountain barriers, rainfall occurs.
SEASON OF RETREATING MONSOONS OR AUTUMN
Winds move back from the mainland to the Bay of Bengal. This is the season of the retreating monsoons. The southern parts of India, particularly Tamil Nadu and Andhra Pradesh receive rainfall in this season.
However, the climate is about the average weather condition, which have been measured over many years. The climate of India has broadly been described as Monsoon type. Monsoon is taken from the Arabic word ‘mausim’, which means seasons. Due to India’s location in the tropical region, most of the rain is brought by monsoon winds. Agriculture in India is dependent on rains. Good monsoons mean adequate rain and a bountiful crop.
Broadly, the major seasons recognised in India are:
- Cold Weather Season (Winter) December to
February
- Hot Weather Season (Summer) March to May
- Southwest Monsoon Season (Rainy)
June to September
- Season of Retreating Monsoon (Autumn) October
and November
The climate of a place is affected by its location, altitude, distance from the sea, and relief. Therefore,
we experience regional differences in the climate of India. Jaisalmer and Bikaner in the desert of Rajasthan are very hot, while Drass and Kargil in Jammu and Kashmir are freezing cold. Coastal places like Mumbai and Kolkata experience moderate climate. They are
neither too hot nor too cold. Being on the coast, these places are very humid. Mawsynram in Meghalaya receives the world’s highest rainfall, while in a particular year it might not rain at all in Jaisalmer in Rajasthan.
The grasses, shrubs and trees, which grow on their own without interference or help from human beings are called natural vegetation. Do you wonder how these differ from each other. Different types of natural vegetation are dependent on different climatic conditions, among which the amount of rainfall is very important.
Due to varied climatic conditions, India has a wide range of natural vegetation. Vegetation of India can be divided into five types – Tropical evergreen forest, Tropical deciduous forest, Thorny bushes, Mountain vegetation and Mangrove forests.
TROPICAL RAIN FOREST
Tropical Rain Forests occur in the areas
which receive heavy rainfall. They are so
dense that sunlight doesn’t reach the ground. Many species of trees are found in these forests, which shed their leaves at different times of the
year. Therefore, they always appear green and are called evergreen forest as you may notice in Figure 8.1. Important trees found in these forests are mahogany, ebony and rosewood. Andaman and Nicobar Islands, parts of North-Eastern states and a narrow strip of the Western slope of the Western Ghats are home of these forests.
TROPICAL DECIDUOUS FORESTS
In a large part of our country we have this type of forest. These forests are also called monsoon forests. They are less dense. They shed their leaves at a particular time of the year. Important trees of these forests are sal, teak, peepal, neem and shisham. They are found in Madhya Pradesh, Uttar Pradesh, Bihar, Jharkhand, Chhattisgarh, Odisha, and in parts of Maharashtra.
THORNY BUSHES
This type of vegetation is found in dry areas of the country. The leaves are in the form of spines to reduce the loss of water. Cactus, khair, babool, keekar are important and are found in the states of Rajasthan, Punjab, Haryana, Eastern slopes of Western Ghats and Gujarat.
MOUNTAIN VEGETATION
A wide range of species is found in the mountains according to the variation in height. With increase in height, the temperature falls. At a height between 1500 metres and 2500 metres most of the trees are conical in shape. These trees are called coniferous trees. Chir, Pine and Deodar are important trees of these forests.
MANGROVE FORESTS
These forests can survive in saline water. They are found mainly in Sunderbans in
West Bengal and in the Andaman and Nicobar Islands. Sundari is a well-known species of trees in mangrove forests after which Sunderbans have been named.
Camels and wild asses are found in the Great Indian desert and the Rann of Kuchchh respectively. Wild goats, snow leopards, bears, etc. are found in the Himalayan region
There are several bird sanctuaries which have been created to give birds their natural habitat. These provide the birds protection from hunters.
Due to cutting of forests and hunting, several species of wildlife of India are declining rapidly. Many species have already become extinct.
In order to protect them many national parks, sanctuaries and biosphere reserves have been set up. The Government has also started Project Tiger and Project Elephant to protect these animals. Can you name some wildlife sanctuaries of India and locate them on a map?
Every year we observe wildlife week in the first week of October, to create awareness of conserving the habitats of the animal kingdom.
Migratory Birds
Some birds such as the Pelican, Siberian Crane, Stork, Flamingo, Pintail Duck and Curlew migrate to our country in the winter season every year. Siberian Cranes migrate from Siberia. They arrive in December and stay till early march.
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